摘要
在压力2.5~4 MPa,质量流量0.7~1.7 g/s,入口温度20~250℃的实验条件下,对煤油在内径1 mm,长度300 mm竖直上升圆管中的流动及传热不稳定现象进行了实验研究.结果表明,当热流密度增大到一定程度后,传热不稳定开始发生.不稳定发生的起始热流密度随压力和流量的增加而增大,随入口油温的升高而减小,且当入口油温升高到一定程度后无不稳定现象发生.不稳定发生的初始时刻,出口油温迅速增加,管道壁温明显下降,传热系数增大;实验段局部流速增大,进而在管道内部形成压力脉动并产生声音.不稳定结束后,出口油温几乎保持不变,壁温会缓慢增加,直至下一次不稳定发生.
The flow and heat transfer instabi lit ies of kerosene flowing in a ver t ical upward circular tube were experimentally investigated. The tube is 1 mm in diameter and 300 mm in length. Pressure ranges from 2.5 - 4 MPa,mass f low rate ranges from 0.7 -1.7 g/s and inlet temperature ranges from 300 -520 K. Results indicate that heat transfer instabi lity appears when the applied heating power exceeds a threshold value. It is found that the instabi lity threshold power increases with the in-creasing of pressure and mass flow rate while it decreases with the increasing of inlet temperature. Heat transfer instabi lity will not happen when inlet temperature reaches a certain value. At the ini tial state of the instabi l ity, the outlet temperature rises rapidly while the temperature of the section wall drops rapidly. Heat transfer coefficient increases during the instabi lity. Increasing of the local flow velocity leads to the pressure pulsation and causes sounds. Af ter the instabi lity, the outlet tem-perature keeps almost constant while the wall temperature keeps rising unti lthe next instabi lity happens.
出处
《气体物理》
2017年第1期57-63,共7页
Physics of Gases
基金
国家自然科学基金(11372348)
关键词
超临界压力传热
传热不稳定
压力脉动
传热强化
superc ritical pressure heat transfer
heat transfer instabi l ity
pressure pulsation
heat transfer enhancement
